A display element including a current drive type light-emitting unit, and a display device including the display element are known. For example, a display element including a light-emitting unit utilizing electroluminescence of an organic material (hereinafter may be simply referred to as an organic EL display element) is noted as a display element capable of high luminance light emission by low voltage direct current drive.
Similarly to a liquid crystal display device, for example, in a display device including the organic EL display element, a simple matrix system and an active matrix system are known as a drive system. The active matrix system has a disadvantage that its structure is complicated, but has an advantage that a luminance of an image can be increased, for example. The organic EL display element driven by the active matrix system includes a light-emitting unit including an organic layer including a light emitting layer and the like, and also includes a drive circuit for driving the light-emitting unit.
For example, Japanese Patent Application Laid-Open No. 2003-223136 (Patent Document 1) and the like describe the use of ramp waveform sloping wave voltage for driving such a display element.